1. Technical Field
The present disclosure relates to a light source device and an image display apparatus using the light source device, and is suitable for, for example, a light source device using a laser light source, and an image display apparatus for displaying an image produced by an image producing unit using the light source device.
2. Description of the Related Art
Development of a laser display device has been advanced that projects an image on a screen using, for example, red, blue, and green laser light. Furthermore, development of an image display apparatus has been recently advanced that displays images in a space by a virtual image optical system combining surface reflection on a glass surface (or a half mirror), a free curved surface mirror, etc.
Specifically, application to an image display apparatus called a head up display mounted on a moving body such as an automobile has been expected. For example, in a head up display mounted on an automobile, the light modulated by image data is projected toward a windshield (front glass), and its reflection light is radiated onto the eyes of an automobile driver.
This allows the automobile driver to see a virtual image on the front side of the windshield. For example, car speed, temperature, etc. are displayed as a virtual image. Recently, it has been also examined to display a navigation image or an image that alert the automobile driver to a real passer as a virtual image.
In the above head up display, a laser light source such as a semiconductor laser can be used as its light source. In such a structure, laser light scans a screen while being modulated depending on an image signal. The laser light is defused on the screen to increase an area of light radiated on the eyes of the automobile driver. This prevents the eyes from being deviated from an irradiation area even when the automobile driver moves his/her head a little, enabling the automobile driver to see a (virtual) image excellently and stably.
Using a laser light source makes it possible to, in addition to downsize an optical system for scanning laser beam on a screen, display a large virtual image regardless of a smaller main body size by combining a virtual image optical system having a large optical magnification, so that the effect of increasing the number of types of automobiles mounting thereon a head up display has been expected.
Japanese Translation of PCT Publication 2008-529069 discloses an image projection apparatus for projecting a two-dimensional color image. The image projection apparatus includes a supporter, a laser assembly for applying a plurality pieces of laser light having different wavelengths, a scanner for sweeping a pattern of a scanning line in a space existing at an action distance from the supporter, a controller for generating an image by making a selected pixel to be applied by the laser light to be seen, and an optical assembly for forming a synthesized light beam to be oriented toward the scanner by making the laser light be focused to substantially align the laser light to be collinear.
Unexamined Japanese Patent Publication No. 2015-194705 discloses head up display device 100 (projector) including laser diodes 11a to 11c, housing unit 7 (base unit 7), and heat sinks 5a and 5b, wherein the heat resistance of a first heat transfer route from laser diode 11a (11b or 11c) to housing unit 7 is larger than the heat resistance of a second heat transfer route from laser diode 11a (11b or 11c) to heat sink 5a or heat sink 5b. 